MR Spectroscopy of the Prostate at 3T: Measurements of Relaxation Times and Quantification of Prostate Metabolites using Water as an Internal Reference

Abstract

Purpose: We performed single-voxel magnetic resonance spectroscopy (MRS) of the human prostate at 3 tesla using a surface coil to measure prostate water, choline (Cho), creatine (Cr), and citrate (Cit) relaxation times T 1 , T 2 , and to estimate concentrations of Cho, Cr, and Cit in healthy volunteers.Methods: In nine of 17 healthy volunteers, we performed experiments to estimate relaxation time, and we used the spectra of the other eight to compute metabolite concentrations. Spectra were processed by LCModel and AMARES (advanced method for accurate, robust, and e‹cient spectralˆtting) algorithms. T 1 and T 2 values were obtained by monoexponentialˆtting of the spectral intensities. Metabolite concentrations were estimated using prostate tissue water as an internal concentration reference.Results: Relaxation times are reported for prostate water (T 1 , 2163±166 ms; T 2 , 110±18 ms), Cho (T 1 , 987±71 ms; T 2 , 239±24 ms), Cr (T 1 , 1128±149 ms; T 2 , 188±20 ms), and Cit (T 1 , 476±70 ms; T 2 , 228±42 ms). Mean concentrations in healthy prostate were Cho, 2.6±0.3 mM, Cr, 5.8±1.3 mM, and Cit, 26.9±5.5 mM.Conclusion: We observed metabolite relaxation times and concentrations consistent with published values of healthy volunteers at 1.5 and 3T. T 1 values increased and T 2 slightly decreased with magneticˆeld strength. Our preliminary patient results indicate that waterreferenced quantitative MRS of the human prostate is a promising tool for monitoring therapeutic eŠects and detecting tumor relapse, i.e., in situations when Cit intensity is small or undetectable.

In vivo proton magnetic resonance spectroscopy of liver metabolites in non-alcoholic fatty liver disease in rats: T2 relaxation times in methylene protons

“…2014). Relaxation time could also be used as a biomarker for determining absolute quantification of all metabolites (Soher et al, 1996;Bakken et al, 2001;Bolan et al, 2003;Yahya et al, 2011;Weis et al, 2013).…”

“…J-coupling interactions are strongly dependent on the choice of multi-TEs, as is assumed by monoexponential function enabling representative T2 relaxation times (Yahya and Fallone, 2010). Accurate T1 and T2 relaxation times that take into account the J-coupling effect may help obtain absolute concentrations using an external reference metabolite of known concentration (Bakken et al, 2001;Li et al, 2005) or an internal quantification method using the ratios of integrals with specific metabolite peaks (i.e., creatine or water) (Christiansen et al, 1993;Soher et al, 1996;Bolan et al, 2003;Tong et al, 2004;Baik et al, 2006;Minati et al, 2010;Weis et al, 2013). Therefore, for absolute quantification of lipid metabolites, it is necessary to accurately measure relaxation time (Michaelis et al, 1993;Hamilton et al, 2011;Gajdošík et al, Fig.…”

Quantification of metabolite concentrations in benign and malignant prostate tissues using 3D proton MR spectroscopic imaging

“…Apparent relaxation time T 1 of Spm was determined by monoexponential fitting of broad polyamine multiplet intensity centered at 3.1 ppm vs. TR by a Levenberg–Marquardt algorithm as implemented in the software package ORIGIN v. 9 (OriginLab, Northampton, MA). The metabolite‐to‐water spectral intensity ratios were corrected for relaxation effects: water ( T 1 , 2163 ± 166 msec; T 2 , 110 ± 18 msec), Cho ( T 1 , 987 ± 71 msec; T 2 , 239 ± 24 msec), and Cit ( T 1 , 476 ± 70 msec; T 2 , 228 ± 42 msec) . It was not possible to measure spermine T 2 by available MRS sequences due to the modulation of the decay curve by phase evolution from homonuclear coupling.…”

“…Approximate T 2 ∼65 msec of the Spm (in vitro prostate tissue at 37°C, B 0 = 11.7 T) was, therefore, taken from the literature . Concentration 40 188 mM of water in the prostate served as the concentration reference . It was assumed that 12 protons contribute to the Spm intensity at 3.1 ppm …”

“…However, quantifications were only recently repeated using 3T scanners. 2D MRSI 18 and single voxel techniques have been applied for Cho, Cr, and Cit estimations in benign and malignant tissues. Spm and myo‐Inositol concentration of healthy tissues, in addition to Cho, Cr, and Cit, were measured by Basharat et al using short time echo 2D MRSI .…”